F14512, a polyamine-vectorized anti-cancer drug, currently in clinical trials exhibits a marked preclinical anti-leukemic activity.

Chemotherapy remains mainly used for the treatment of acute myeloid leukemia (AML). However, in the past 3 decades limited progress has been achieved in improving the long-term disease-free survival. Therefore the development of more effective drugs for AML represents a high level of priority. F14512 combines an epipodophyllotoxin core targeting topoisomerase II with a spermine moiety introduced as a cell delivery vector. The polyamine moiety facilitates F14512 selective uptake by tumour cells via the polyamine transport system, a machinery overactivated in cancer cells. F14512 has been characterized as a potent drug candidate and is currently in Phase I clinical trials. Here, we demonstrated marked survival benefit and therapeutic efficacy of F14512 treatments in a series of human AML models, established either from AML cell lines or from patient AML samples. Furthermore, we reported in vitro synergistic anti-leukemic effects of F14512 in combination with cytosine arabinoside (Ara-C), doxorubicin, gemcitabine, bortezomib or SAHA. In vivo combination of suboptimal doses of F14512 with Ara-C also resulted in enhanced anti-leukemic activity. We further showed that F14512 triggered both senescence and apoptosis in vivo in primary AML models, but not autophagy. Overall, these results support the clinical development in onco-hematology of this novel promising drug candidate.

A fluorescent biomarker of the polyamine transport system to select patients with AML for F14512 treatment.

The polyamine transport system (PTS), hyperactive in cancer cells, can constitute a gate to deliver F14512, a novel spermine epipodophyllotoxin conjugate recently selected for clinical development in AML phase I. We investigated in vitro the high antiproliferative effect of F14512 against 13 leukemia cell lines, and demonstrated a statistically significant correlation with the level of PTS activity, using a novel fluorescent marker F96982. This labelling protocol was then adapted for clinical applications for blood, bone marrow and AML samples with CD45 gating. Within the patient samples, the PTS activity varied significantly in AML cells, as compared to normal lymphocytes. In conclusion, the identification of PTS-positive AML with F98982 probe offers new perspectives to select patients prone to respond to F14512.

F 11782, a dual inhibitor of topoisomerases I and II with an original mechanism of action in vitro, and markedly superior in vivo antitumour activity, relative to three other dual topoisomerase inhibitors, intoplicin, aclarubicin and TAS-103.

PURPOSE: F 11782 (2",3"-bis pentafluorophenoxyacetyl-4",6"-ethylidene-beta-D-glucoside of 4'-phosphate-4'-dimethylepipodophyllotoxin, di-N-methyl glucamine salt) is a newly synthesized dual catalytic inhibitor of topoisomerases I and II with major in vivo antitumour activity. In this study, we compared and contrasted F 11782 with three other known inhibitors of both these nuclear enzymes, namely aclarubicin. intoplicin and TAS-103, and established its novel mechanism of action. METHODS: In vitro growth-inhibitory effects against a panel of murine and tumour cell lines were measured by cell counting, clonogenicity or tetrazolium metabolic dye (MTT) assays. In vivo antitumour activities were evaluated against two murine tumour models (i.v. P388 leukaemia and s.c. B16 melanoma). Finally, interactions with either DNA or DNA-topoisomerases were determined using various methodologies: DNA-intercalator displacement, pBR322 DNA relaxation, kDNA decatenation, topoisomerase II extractability measurements, stabilization of topoisomerase-induced cleavable complexes (CC) in vitro and in cells, and gel retardation assays. RESULTS: F 11782 had a different profile of sensitivities and proved generally less cytotoxic than the other dual inhibitors tested in vitro, while showing significantly superior antitumour activity in vivo. F 11782, which did not stabilize CC either in vitro or in cells, was the only compound of this series capable of inhibiting the catalytic activity of both DNA-topoisomerases without interacting with DNA, and of completely impairing the binding of these nuclear proteins to DNA. Moreover, only cotreatment of cells in vitro with F 11782 enhanced the cytotoxic activity of etoposide. CONCLUSION: These results emphasize the novel mechanism of action of F 11782 vis-a-vis the other dual inhibitors of topoisomerases I and II and so augur well for its future clinical development.

Synthesis and antitumor activity of new glycosides of epipodophyllotoxin, analogues of etoposide, and NK 611.

A series of 3-amino- and 3-alkylamino-2-deoxy-beta-D-ribo- and beta-D-arabino-glycosides of 4'-demethylepipodophyllotoxin have been synthesized by means of an improved trimethylsilyliodide procedure for the podophyllotoxin-4'-demethylepipodophyllotoxin conversion, an efficient and high yielding synthesis of silyl glycoside donors of 3-azido-2,3-dideoxy-beta-D-ribo- and beta-D-arabino-hexopyranosides and stereoselective glycosylations. In vitro evaluation of cytotoxic effects against murine L1210 leukemia critically demonstrates the essential role played by a 4,6-acetal for biological activity. Among the most cytotoxic compounds, 3-amino-2,3-dideoxy- and 3-N, N-(dimethylamino)-2,3-dideoxy etoposide analogues, 17 and 27-29 are at least as potent as etoposide on the in vivo P388 (iv/ip) murine leukemia models. However, surprisingly enough, none of these compounds inhibits the human DNA topoisomerases I or II or binds to tubulin to prevent its polymerization and microtubule assembly. Therefore, their mechanism of action remains to be cleared up.

Requirements for P-glycoprotein recognition based on structure-activity relationships in the podophyllotoxin series.

Podophyllotoxin and epipodophyllotoxin react with tubulin at the same binding site as colchicine, but in contrast to colchicine, do not appear to exert their cytotoxicities by mechanisms dependent on P-glycoprotein (Pgp) expression. To investigate structural requirements for Pgp recognition a series of podophyllotoxin and epipodophyllotoxin derivatives have been synthesized. Their interactions with the multidrug resistance-related protein Pgp have been studied by evaluating their relative cytotoxicities versus P388-sensitive murine leukemic cells and a classic multidrug-resistant (MDR) Pgp-overexpressing subline (P388/ADR), and their relative tubulin polymerization inhibitory activities against microtubular proteins have been determined. Based on tridimensional structure-activity relationships within this series of compounds, structural requirements for Pgp recognition have been identified. Moreover, proposals are made for extending these criteria to other chemical classes of anticancer drugs.

[(125I)iodo-zacopride: new ligand for the study by autoradiography of central 5-HT3 receptors]. / [125I]iodo-zacopride: un nouveau ligand pour l'étude par autoradiographie des récepteurs 5-HT3 centraux.

This paper describes the synthesis and the pharmacological characteristics of the first radioiodinated ligand of central 5-HT3 receptors: [125I]iodo-zacopride. Specific sites having a high affinity (Kd = 4.3 nM) for [125I]iodo-zacopride have been found in membranes from the rat entorhinal cortex. In addition, a highly significant correlation (r = 0.995) existed between the Ki of several 5-HT-related drugs for displacing both [125I]iodo-zacopride from its specific binding sites, and [3H]zacopride from 5-HT3 receptors. Finally, [125I]iodo-zacopride was successfully used for the autoradiographic mapping of 5-HT3 receptors in the rat central nervous system.